Contention control mechanism

ABSTRACT

Methods, systems, and devices are described for enhanced network utilization between an access point and a number of wireless stations. A station (STA), following a transmit opportunity (TXOP), may determine a utilization of the TXOP. Based on the determination, the STA may adjust a delay time for a subsequent transmission. The adjustment of the delay time may include increasing an initial contention window (CW), increasing a backoff value, and/or increasing a number of backoffs for TXOPs following an underutilized TXOP. The increased delay time may result in, on average, increased backoff times in such situations. The delay time may be reduced to a minimum delay time following a certain number of TXOPs that more fully utilize the TXOP. Utilization of the TXOP may be determined based on an amount of time used for the TXOP relative to a TXOP limit that may be set by an access point.

CROSS REFERENCES

The present application for patent claims priority to U.S. ProvisionalPatent Application No. 61/844,261 by Wentink, entitled “ContentionControl Mechanism,” filed Jul. 9, 2013, assigned to the assignee hereof,and expressly incorporated by reference herein. The present applicationfor patent also claims priority to U.S. Provisional Patent Application61/844,834 by Wentink, entitled “Contention Control Mechanism,” filedJul. 10, 2013, assigned to the assignee hereof, and expresslyincorporated by reference herein.

BACKGROUND

Wireless communications networks are widely deployed to provide variouscommunication services such as voice, video, packet data, messaging,broadcast, and the like. These wireless networks may be multiple-accessnetworks capable of supporting multiple users by sharing the availablenetwork resources.

A wireless communications network may include a number of networkdevices such as access points (APs) that can support communication for anumber of wireless stations. A wireless station (STA) may communicatewith a network device bidirectionally. For example, in a wireless localarea network (WLAN), a STA may communicate with an associated AP viadownlink and uplink. The downlink (or forward link) refers to thecommunication link from the AP to the STA, and the uplink (or reverselink) refers to the communication link from the STA to the AP.

In WLANs, there may be cases in which multiple STAs are in communicationwith a particular AP. Access to the wireless medium may be controlledthrough a medium access control (MAC), which may allow different STAs toaccess a wireless channel according to enhanced distributed channelaccess (EDCA) rules. Included in the EDCA rules is a transmitopportunity (TXOP) limit, which is a duration of time during which a STAis allowed to continually access the medium without backoff. In somedeployments, a wireless network may have four different accesspriorities according to an access class (AC) of data that is transmittedusing the wireless channel, each of which may have a different TXOPlimit.

In order to enhance utilization of the wireless network, it would bedesirable for different STAs accessing the wireless network to utilizerelatively fewer TXOPs with each containing more data for transmissionrather than relatively more TXOPs with each containing less data fortransmission, while still maintaining quality of service (QoS) criteriafor a particular AC of data.

SUMMARY

Various methods, systems, devices, and apparatuses are described forenhanced network utilization in a wireless communications system throughefficient transmissions of information between an access point (AP) anda station (STA). A STA in a wireless communications network may,following a transmit opportunity (TXOP), determine a utilization of theTXOP. Based on the determination, the STA may adjust a delay time for asubsequent transmission. The adjustment of the delay time may includeincreasing an initial contention window (CW) size, increasing a backoffvalue, and/or increasing a number of backoffs for TXOPs following anunderutilized TXOP. An increase in the initial CW may result in, onaverage, increase in backoff times, which may lead to increase in theamount of data that is transmitted in the subsequent TXOP and therebyenhance network utilization. The delay time may be reduced to a minimumdelay time following a certain number of TXOPs that more fully utilizethe TXOP. Utilization of the TXOP may be determined based on an amountof time used for the TXOP relative to a TXOP limit that may be set by anAP.

According to an aspect of the disclosure, a method for wirelesscommunications is provided. The method generally includes determining autilization of a transmit opportunity (TXOP) during a transmission ofdata from a wireless communication device, and adjusting a delay timefor a subsequent transmission from the wireless communication devicebased on the determined utilization. Adjusting the delay time mayinclude, for example, increasing an initial CW value, increasing abackoff value, and/or increasing a number of backoffs, when theutilization is less than a predetermined utilization. Adjusting may alsoinclude decreasing the delay time when the utilization is greater than apredetermined utilization, or decreasing the delay time when theutilization is greater than a predetermined utilization and theutilization of a predetermined number of previous TXOPs are each greaterthan the predetermined utilization.

In some examples, the determining may include determining a timeduration during which data is transmitted during a transmit opportunity(TXOP) and adjusting the delay time by increasing the delay time whenthe time duration is shorter than a predetermined time duration. Inother examples, the determining may include determining a maximumduration of the TXOP, determining a time duration during which data istransmitted during the TXOP, and determining a ratio of the timeduration and the maximum duration. In some such examples, adjusting thedelay time may include increasing the delay time when the ratio is lessthan a predetermined ratio. Additionally or alternatively, adjusting thedelay time may include one or more of adjusting the delay time to allowfor accumulation of additional data prior to the subsequent transmissionrelative to an amount of data accumulated using an unadjusted delay timeor scaling the delay time according to the utilization of the TXOP.

In some examples, adjusting the delay time may include increasing thedelay time by a first amount when the utilization is less than apredetermined utilization, and increasing the delay time by a secondamount when the utilization of a subsequent TXOP is less than thepredetermined utilization. In other examples, the method may alsoinclude determining a second utilization of a subsequent TXOP during thesubsequent transmission of data from a wireless communication device,and re-adjusting the delay time responsive to the utilization and secondutilization. Re-adjusting the delay time may include, for example,resetting the delay time to a minimum value when the second utilizationis greater than a predetermined utilization, or further increasing thedelay time when the second utilization is less than a predeterminedutilization.

Another aspect of the disclosure provides an apparatus for wirelesscommunications. The apparatus generally includes means for determining autilization of a transmit opportunity (TXOP) during a transmission ofdata from a wireless communication device, and means for adjusting adelay time for a subsequent transmission from the wireless communicationdevice based on the determined utilization. The means for adjusting theCW value may include, for example, one or more of means for increasing aCW value, increasing a backoff value, or increasing a number of backoffswhen the utilization is less than a predetermined utilization. The meansfor adjusting may also include, for example, means for decreasing thedelay time when the utilization is greater than a predeterminedutilization, means for decreasing the delay time when the utilization isgreater than a predetermined utilization and the utilization of apredetermined number of previous TXOPs are each greater than thepredetermined utilization, means for scaling the delay time according tothe utilization of the TXOP, or means for increasing the delay time by afirst amount when the utilization is less than a predeterminedutilization and increasing the delay time by a second amount when theutilization of a subsequent TXOP is less than the predeterminedutilization.

In some examples, the means for determining may include means fordetermining a time duration during which data is transmitted during atransmit opportunity (TXOP). In some of such examples, the means foradjusting the delay time may include means for increasing the delay timewhen the time duration is shorter than a predetermined time duration. Inother examples, the means for determining may include means fordetermining a maximum duration of the TXOP, means for determining a timeduration during which data is transmitted during the TXOP, and means fordetermining a ratio of the time duration and the maximum duration. Insome of such examples, the means for adjusting the delay time mayinclude means for increasing the delay time when the ratio is less thana predetermined ratio.

In some examples, the apparatus may also include means for determining asecond utilization of a subsequent TXOP during the subsequenttransmission of data from a wireless communication device, and means forre-adjusting the delay time responsive to the utilization and secondutilization. The means for re-adjusting the delay time may include, forexample, means for resetting the delay time to a minimum value when thesecond utilization is greater than a predetermined utilization, or meansfor further increasing the delay time when the second utilization isless than a predetermined utilization.

In another aspect, an apparatus for wireless communication is provided.The apparatus generally includes a receiver configure to receivewireless communications form an access point and a transmitterconfigured to transmit data to the access point during a transmitopportunity (TXOP). The apparatus also includes a delay time managerconfigured to determine a utilization of a transmit opportunity (TXOP)during a transmission of data from a wireless communication device, andadjust a delay time for a subsequent transmission from the wirelesscommunication device based on the determined utilization.

In certain examples, the apparatus for wireless communication may beconfigured to implement one or more aspects of the functionalitydescribed above with reference to the method for wirelesscommunications.

In another aspect, a non-transitory computer readable medium is providedhaving computer-readable program code stored thereon that when executedby at least one processor causes the at least one processor to determinea utilization of a transmit opportunity (TXOP) during a transmission ofdata from a wireless communication device and adjust a delay time for asubsequent transmission from the wireless communication device based onthe determined utilization.

In certain examples, the computer-readable program code may furthercause the at least one processor to perform one or more aspects of thefunctionality described above with reference to the method for wirelesscommunications.

The foregoing has outlined rather broadly the features and technicaladvantages of examples according to the disclosure in order that thedetailed description that follows may be better understood. Additionalfeatures and advantages will be described hereinafter. The conceptionand specific examples disclosed may be readily utilized as a basis formodifying or designing other structures for carrying out the samepurposes of the present disclosure. Such equivalent constructions do notdepart from the scope of the appended claims. Features which arebelieved to be characteristic of the concepts disclosed herein, both asto their organization and method of operation, together with associatedadvantages will be better understood from the following description whenconsidered in connection with the accompanying figures. Each of thefigures is provided for the purpose of illustration and descriptiononly, and not as a definition of the limits of the claims.

BRIEF DESCRIPTION OF THE DRAWINGS

A further understanding of the nature and advantages of the presentdisclosure may be realized by reference to the following drawings. Inthe appended figures, similar components or features may have the samereference label. Further, various components of the same type may bedistinguished by following the reference label by a dash and a secondlabel that distinguishes among the similar components. If only the firstreference label is used in the specification, the description isapplicable to any one of the similar components having the same firstreference label irrespective of the second reference label.

FIG. 1 shows a diagram that illustrates an example of a wireless localarea network (WLAN) that supports enhanced network utilization accordingto various examples;

FIG. 2 shows a diagram that illustrates an example of a frame exchangebetween an access point (AP) and a station (STA) according to variousexamples;

FIG. 3 shows a diagram that illustrates an example of data transmissionbetween an AP and a STA according to various examples;

FIG. 4 is a flowchart of an example of operations related to adjusting acontention window (CW) for wireless channel access according to variousexamples;

FIG. 5 is another flowchart of an example of operations related toadjusting a CW for wireless channel access according to variousexamples;

FIG. 6 is another flowchart of an example of operations related toadjusting a CW for wireless channel access according to variousexamples;

FIG. 7 shows a block diagram that illustrates an example of anarchitecture for adjusting CW according to various examples;

FIG. 8 shows a block diagram that illustrates an example of a STAarchitecture according to various examples;

FIG. 9 shows a block diagram that illustrates an example of an AParchitecture according to various examples;

FIG. 10 is a flowchart of an example of a method for delay timeadjustment in a wireless communication system according to variousexamples;

FIG. 11 is a flowchart of an example of another method for delay timeadjustment in a wireless communication system according to variousexamples;

FIG. 12 is a flowchart of an example of yet another method for delaytime adjustment in a wireless communication system according to variousexamples; and

FIG. 13 is a flowchart of an example of a method for dynamic control ofdelay time in a wireless communication system according to variousexamples.

DETAILED DESCRIPTION

Described examples are directed to methods, systems, devices, andapparatuses for accessing a wireless channel in a wirelesscommunications network that may enhance network utilization and powerconservation through efficient transmissions of information between anaccess point (AP) and a station (STA). A STA in a wirelesscommunications network may, following a transmit opportunity (TXOP),determine a utilization of the TXOP. Utilization, in some cases, may bedetermined based on an amount of time used for the TXOP relative to aTXOP limit that may be set by the AP. Based on the determination, theSTA may adjust a delay time for a subsequent transmission. Theadjustment of the delay time may include increasing or decreasing aninitial contention window (CW) size, increasing or decreasing a backoffvalue, and/or increasing or decreasing a number of backoffs for TXOPsfollowing an underutilized TXOP or a fully utilized TXOP. In the case ofthe underutilized TXOP, the delay time may be increased by increasingthe initial CW size. This may result in, on average, increase in backofftimes, which may lead to an increase in the amount of data to betransmitted in the subsequent TXOP thereby enhancing networkutilization. For the fully utilized TXOP, in some cases, the initialdelay time may be reduced to a minimum delay time following a certainnumber of TXOPs that more fully utilize the TXOP.

The channel access techniques presented herein are generally describedin connection with WLANs for simplicity. A WLAN (or Wi-Fi network) mayrefer to a network that is based on the protocols described in thevarious IEEE 802.11 standards (e.g., 802.11a/g, 802.11n, 802.11ac,802.11ah, etc.). The same or similar techniques, however, may be usedfor various other wireless communications systems such as cellularwireless systems, peer-to-peer wireless communications, ad hoc networks,satellite communications systems, and other systems. The terms “system”and “network” may be used interchangeably.

Thus, the following description provides examples, and is not limitingof the scope, applicability, or configuration set forth in the claims.Changes may be made in the function and arrangement of elementsdiscussed without departing from the scope of the disclosure. Variousexamples may omit, substitute, or add various procedures or componentsas appropriate. For instance, the methods described may be performed inan order different from that described, and various steps may be added,omitted, or combined. Also, features described with respect to certainexamples may be combined in other examples.

Referring first to FIG. 1, a wireless communications network 100, suchas WLAN or Wi-Fi network is shown that is configured to provide enhancednetwork utilization according to the aspects of the disclosure. The WLANnetwork 100 includes an AP 105 and multiple associated STAs 115. In thisexample, there are shown seven (7) STAs 115, which are identified asSTA_1, STA_2, STA_3, STA_4, STA_5, STA_6, and STA_7. The WLAN network100, however, may have more or fewer STAs 115 than those shown in FIG. 1since the number shown is simply for illustrative purposes. The AP 105and the associated STAs 115 may represent a basic service set (BSS). Thevarious STAs 115 in the BSS are able to communicate with one anotherthrough the AP 105. Also shown is a coverage area 120 of the AP 105,which may represent a basic service area (BSA) of the WLAN network 100.Although not shown in FIG. 1, the BSS associated with the WLAN 100 istypically connected to a wired or wireless distribution system (DS) thatallows multiple APs to be connected in an extended service set.

The AP 105 is configured to communicate bi-directionally with each ofthe STAs 115 using transmissions 130. The transmissions 130 may includedownlink transmissions (e.g., beacon frames) that are sent from the AP105 to a STA 115 as well as uplink transmissions of data frames that aresent from a STA 115 to the AP 105, which are referred to as transmissionopportunities (TXOPs). Simultaneous transmissions by different STAs 115over the wireless medium in the wireless communications network 100 mayresult in collisions between the transmissions which may degrade theefficiency of the wireless communications network 100. Collisionsbetween STAs 115 may be resolved according to contention mechanisms thatresult in the STAs 115 attempting to retransmit a communicationfollowing a backoff period, as will be described in more detail below. ASTA 115 that sends many short TXOPs separated by a backoff will have amuch higher contention activity than a STA 115 that groups traffic intolonger but fewer TXOPs. In various examples, the latter may beimplemented according to various techniques for adjusting a delay timeprior to initiating a subsequent transmission following an underutilizedTXOP, as will be described in more detail below. Such delay timeadjustment may result in relatively fewer TXOPs that may result in lesscontention and therefore fewer collisions. This may result in enhancednetwork efficiency, as well as reduced power consumption at both theSTAs 115 and AP 105.

With reference now to FIG. 2, an example 200 of transmissions between aSTA 115-a and an AP 105-a is described. The STA 115-a and AP 105-a maybe examples of STAs 115 and AP 105 of FIG. 1. In the example shown, theSTA 115-a is assumed to have completed a TXOP as indicated at block 205.In response to a successfully received transmission, the AP 105-a maytransmit an acknowledgment 210 to the STA 115-a. According to oneexample, for each successfully received frame, the AP 105-a may send anacknowledgement (ACK) frame after a short interframe space (SIFS), whichis shorter than the DIFS, and thus does not result in other stationsattempting to gain access to the medium. Other stations resume thebackoff process after the DIFS idle time. In the absence of the ACKframe, the STA may determine that the transmission was not successful inwhich case the STA 115-a may retransmit the data after another randombackoff. After determining that the data was transmitted successfully ornot, the STA 115-a may set a contention window (CW) size and a backoffcounter based on the CW size, as indicated at block 215. The backoffcounter may be determined as a random integer drawn from a uniformdistribution over the interval [0,CW]. The CW size, according to variousexamples, may be calculated according to different techniques in orderto enhance network efficiency while maintaining required Quality ofService (QoS) for a given access class (AC), as will be described infurther detail below. If the channel becomes busy during a backoffprocess, the backoff counter may be suspended. When the channel becomesidle again, and stays idle for an extra distributed coordinationfunction (DCF) interframe space (DIFS) time interval, the backoffprocess resumes with the suspended backoff counter value.

Following the expiration of the backoff counter, the STA 115-a may,according to the example of FIG. 2, transmit a request to send (RTS) 220to the AP 105-a. In the event that there is no collision with anotherSTA, the AP 105-a of this example may send a clear to send (CTS)indication 225 to the STA 115-a. Such RTS/CTS transmissions may beimplemented in some examples to reduce frame collisions, although otherexamples may not implement RTS/CTS communications. The STA 115-a maythen transmit data to the AP 105-a as indicated at 230. Following theTXOP limit, or the transmission of all of the data in a buffer at theSTA 115-a, the TXOP is assumed to be completed as indicated by block235, and the process then repeats.

In some examples, the CW may be set (or reset) after a successful TXOPto a minimum CW size (CWmin), where CWmin is the minimum CW for the ACfor which the TXOP was obtained. The CW that is used after a successfulTXOP is referred to as the initial CW. In various examples describedherein, the delay time from completion of a TXOP to the start of asubsequent TXOP may be adjusted to enhance efficiency of the network byusing one or a number of mechanisms. For example, the delay time may beadjusted, by adjusting an initial CW for subsequent transmissions, byadjusting a backoff value directly for subsequent transmissions, and/orby adjusting a number of backoffs before initiating a subsequent TXOP.In case of an unsuccessful transmission, the delay time may be increasedby increasing the CW per the Enhanced Distributed Channel Access (EDCA)rules. For example, following an unsuccessful transmission attempt,another backoff is performed using a new CW value updated by 2*(CW+1)−1,with an upper bound of CWmax. CWmin and CWmax may be set by the AP 105-aaccording to a particular AC and QoS requirements of the different ACs.The new CW value and selected backoff time reduces the collisionprobability in case there are multiple STAs attempting to access thechannel.

With reference now to FIG. 3, an example 300 of transmissions between aSTA 115-b and an AP 105-b, such as between STA 115 and AP 105 of FIG. 1or 2, according to various examples is described. In this example, theSTA 115-b and the AP 105-b may implement RTS/CTS techniques discussedabove, and a collision may occur in a RTS transmission, resulting in anew CW being set and new backoff counter being established. In otherexamples that do not utilize RTS/CTS techniques, a STA 115-b mayinitiate a TXOP directly, and in the absence of an ACK from the AP 105-bfollowing a first frame, the STA 115-b may determine that a collisionhas occurred. In the example of FIG. 3, the AP 105-b is shown to send aCTS 305 to the STA 115-b. After a SIFS, 310, the STA may initiate TXOP315 to transmit data for a duration of up to a TXOP limit that isestablished by the AP 105-b. In the event that the STA 115-b does nothave enough data in its buffer to transmit during the assigned TXOPduration, the TXOP may end before the TXOP limit is reached. Asmentioned above, however, such shorter transmissions may degrade networkefficiency. Following TXOP 315, a backoff period may be determined. Thebackoff period may be determined in a number of manners, according tovarious examples. According to some examples, a backoff value may be setdirectly following a TXOP, and the backoff value may be adjusted toprovide longer or shorter time delays based on the utilization of TXOP315. In other examples, a number of backoff periods may be performedprior to initialization of a subsequent TXOP, with the number ofbackoffs adjusted based on the utilization of TXOP 315. In furtherexamples, an initial CW size may be set based on the utilization of TXOP315. For example, if the STA 115-b did not transmit data for apredetermined threshold of the TXOP limit, the initial CW size may beincreased, thereby potentially increasing the backoff period before asubsequent TXOP. While many of the examples provided herein are directedto the adjustment of a delay time for one or more subsequent TXOPs, theconcepts described in such examples apply to other techniques foradjusting the delay time prior to one or more subsequent TXOPs, as willbe readily recognized by one of skill in the art.

With continuing reference to FIG. 3, the STA 115-b may transmit a RTS325 following the expiration of the backoff counter and wait a SIFS 330period for a CTS 335 from the AP 105-b. However, because in this examplea collision with a RTS from another STA have occurred, the STA 115-bdoes not receive the CTS 335. As a result, the STA 115-b sets a newbackoff period 340 from a new CW size that is based on the initial CWsize. Following the expiration of the backoff period 340, the STAtransmits another RTS 345. Again, the STA 115-b waits during a SIFS 350period for a CTS 355 from the AP 105-b. Once the STA 115-b receives theCTS 355 from the AP 105-b, the STA 115-b waits for another SIFS period360, before it begins TXOP 365. In the event that multiple collisionsoccur, the CW may be increased a number of times up to a value of CWmax,which may be set by the AP based on, for example, an AC of the data thatis being transmitted.

With reference now to FIG. 4, a flow diagram of a method 400 foradjusting an initial CW size at a STA is discussed in accordance withvarious examples. In the example method shown in FIG. 4, a new CW may beobtained by scaling the initial CW based on the actual utilization ofthe TXOP. In particular, the method disclosed provides for scaling theinitial CW when the TXOP is underutilized, which may be the case whenthe TXOP is too long relative to an actually realized TXOP (i.e. therealized TXOP is too short) or when the TXOP is fully utilized, whichmay be the case when the realized TXOP duration exceeds a certain presetthreshold (i.e. the realized TXOP is too long). The method 400 may beimplemented using, for example, the STA 115 of FIGS. 1-3, or devices ofFIGS. 7-8 discussed below. As shown in the figure, the method begins atblock 405, with the STA transmitting an RTS frame. At block 410, the STAdetermines if a CTS is received. If the STA determines that the CTS isnot received, the STA increases the CW according to usual collisionavoidance techniques, up to a limit of CWmax, as indicated at block 415.The STA then waits for a backoff counter that is set based on the CW toexpire, as indicated at block 420, and proceeds to execute the operationshown at block 405. If, on the other hand, the STA determines that theCTS is received, it begins to transmit data to the AP during a TXOP, asindicated at block 425. At block 430, the STA determines a utilizationof the TXOP. In some examples, the TXOP utilization may be determinedbased on a TXOP limit duration as compared to a duration of datatransmitted (i.e. realized TXOP) at block 425. In other examples, theTXOP utilization may be determined based on an amount of datatransmitted during the TXOP as compared to a theoretical maximum amountof data that could be transmitted during the TXOP.

At block 435, the STA determines if the TXOP utilization is greater thana preset threshold. In some examples, the preset threshold may be set bythe AP based on AC of the data being transmitted and/or current networkconditions. The preset threshold may, according to some examples, be setto 80% of the TXOP limit. If the TXOP utilization is less than thethreshold, indicating that the TXOP is being underutilized, the STA mayadjust the initial CW based on CWmin and the determined TXOPutilization, as indicated at block 440. In some examples, the adjustedinitial CW may be set the CWmin value scaled by the actual TXOPutilization, according to the following formula:

${{adjusted}\mspace{14mu}{initial}\mspace{14mu}{CW}} = {{CW}\;\min \times \frac{{TXOP}\mspace{14mu}{limit}}{{realized}\mspace{14mu}{TXOP}\mspace{14mu}{duration}}}$The adjusted initial CW will thus result in a larger CW, which onaverage will cause a longer backoff, and thereby allow more data trafficto be accumulated before the next TXOP. This in turn may cause thesubsequent TXOP to be longer and thereby enhance the networkutilization. The STA may proceed to execute the operation indicated atblock 420 following the adjustment of CW.

At block 445, if the TXOP utilization is greater than the threshold, theSTA may determine if the TXOP utilization was greater than the presetthreshold for the last X number of TXOPs. According to one example, Xmay be set to 10, although the value of X may be set to any other valueor may be adaptively set by the AP based on current network conditions.In the event the last X TXOPs were not greater than the threshold, theinitial CW may be left at the adjusted initial CW, as indicated at block450. Following the adjustment of the CW, which in the case of the TXOPexceeding the threshold corresponds to a reduction in the CW size, theSTA may proceed to execute the operation indicated at block 420. If, onthe other hand, it is determined that the last X TXOPs were greater thanthe TXOP threshold, the initial CW may be set to CWmin corresponding tothe particular AC of the data being transmitted, as indicated at block455. In this manner, a hysteresis is implemented to increase the initialCW in the event a STA is transmitting short bursts of data (i.e. therealized TXOP is too short), while the CW may be set back to CWmin whenthe STA is transmitting full TXOPs (i.e. the realized TXOP durationexceeds or is equal to a preset threshold).

With reference now to FIG. 5, a flow diagram of another method 500 foradjusting an initial CW size at a STA is shown. The CW may serve as aninitial CW, which means that it is used for the initial transmission ofa frame (i.e. not a retransmission of a frame). According to the examplemethod of FIG. 5, a CW may be adjusted to a predetermined larger initialCW in the event that the TXOP is underutilized. The method 500 may beimplemented using, for example, the STAs 115 of FIGS. 1-3, or devices ofFIGS. 7-8 discussed below. As shown in the figure, the method begins atblock 505, with the STA transmitting an RTS frame. At block 510, the STAdetermines if a CTS is received. If the STA determines that a CTS is notreceived, the STA increases the CW according to usual collisionavoidance techniques, up to a limit of CWmax, as indicated at block 515.The STA then waits for a backoff counter that is set based on the CW toexpire, as indicated at block 520, and proceeds to execute the operationindicated at block 505. If the STA does receive a CTS, it transmits dataduring a TXOP to the AP, as indicated at block 525. At block 530, theSTA determines a utilization of the TXOP. As discussed above, accordingto some examples the TXOP utilization may be determined based on a TXOPlimit duration as compared to a duration of data transmitted at block525. In other examples, the TXOP utilization may be determined based onan amount of data transmitted during the TXOP as compared to atheoretical maximum amount of data that could be transmitted during theTXOP.

At block 535, the STA determines if the utilization is greater than apreset threshold. In some examples, the preset threshold may be set bythe AP based on AC and/or current network conditions. The presetthreshold, for examples, may be set to 80% of the TXOP limit, similarlyas discussed above. If the TXOP utilization is less than the threshold,the STA may adjust the initial CW by setting the adjusted CW to2*(CWmin+1)−1, as indicated at block 540, causing the adjusted initialCW to be larger when the TXOP is not sufficiently long. This may lead toan on average longer backoff, which in turn would allow more datatraffic to be accumulated before the next TXOP causing the subsequentTXOP to be longer, and thus resulting in an enhanced networkutilization. After adjusting the initial CW, the STA may then proceed toexecute the operation specified at block 520.

If the TXOP utilization is determined to be greater than the presetthreshold at block 535, the STA may proceed to determine if the TXOPexceeded the threshold for the last X number of TXOPs, as indicated atblock 545. As discussed above, X may be set to 10, although the value ofX may be set to any other value or may be adaptively set by the AP basedon current network conditions. If the last X TXOPs were not greater thanthe threshold, the initial CW may be left at the adjusted initial CW, asindicated at block 550, and operations are continued at block 520. Ifthe last X TXOPs were greater than the TXOP threshold, the initial CWmay be set to the CWmin for the particular AC of the data beingtransmitted, as indicated at block 555. Again, a hysteresis isimplemented to increase the initial CW in the event a STA istransmitting short bursts of data, and allowing for the initial CW to beset back to CWmin when the STA is transmitting full TXOPs.

In still further examples, the CW may be adjusted in more than one stepto increase an initial CW size following multiple underutilized TXOPs,and may also be adjusted in more than one step to a reduced the initialCW size following one or more TXOPs that are more fully utilized. FIG. 6illustrates a method 600 of an example that uses two steps to increasethe initial CW size. The method 600 may be implemented using, forexample, the STAs 115 of FIGS. 1-3, or devices of FIGS. 7-8 discussedbelow. As shown in the figure, the method begins at block 605, with theSTA transmitting an RTS frame. At block 610, the STA determines if a CTSis received. If a CTS is not received, the STA may increase the CWaccording to usual collision avoidance techniques, up to a limit ofCWmax, as indicated at block 615. The STA may then wait for a backoffcounter that is set based on the CW to expire, as indicated at block620, and proceed to execute the operation indicated at block 605. In theevent the STA does receive a CTS, it may proceed to transmit data duringa TXOP to the AP, as indicated at block 625. Following the TXOP, the STAmay determine a utilization of the TXOP as indicated at block 630. Asdiscussed above, in some examples, the TXOP utilization may bedetermined based on a TXOP limit duration as compared to a duration ofdata transmitted at block 625. In other examples, the TXOP utilizationmay be determined based on an amount of data transmitted during the TXOPas compared to a theoretical maximum amount of data that could betransmitted during the TXOP.

At block 635, the STA determines if the utilization is less than apreset threshold. In some examples, the preset threshold may be set bythe AP based on the AC and/or current network conditions. The presetthreshold in some examples may be set to 80% of the TXOP limit,similarly as discussed above. If the TXOP utilization is at or above thethreshold, the STA may determine if the TXOPs were greater than thethreshold for the last X number of TXOPs, as indicated at block 640. Insome examples, X may be set to 10, but the value of X may be set to anyother value or may be adaptively set by the AP based on current networkconditions. If the last X TXOPs were not greater than the threshold, theinitial CW may be left at the adjusted initial CW, as indicated at block645, and operations may continue at block 620. If the last X TXOPs aregreater than the TXOP threshold, the initial CW may be set to CWmin forthe particular AC of data being transmitted, as indicated at block 650.

In the event the STA determines at block 635 that TXOP utilization wasless than the threshold, the STA may then proceed to determine if theTXOP is the first TXOP that is less than the threshold, as indicated atblock 655. If the TXOP is the first TXOP that is less than thethreshold, the STA may adjust the initial CW, such that the adjustedinitial CW is determined according to 2*(CWmin+1)−1, as indicated atblock 660, and operations may continue with block 620. If the TXOP isnot the first TXOP that is less than the threshold, the STA may furtheradjust the initial CW, such that the adjusted initial CW is determinedaccording to 4*(CWmin+1)−1, as indicated at block 665, and operationsmay continue with block 620. The initial CW may thus be adjusted in twosteps, which will result in larger contention windows based on theparticular traffic of the STA, which on average will cause a longerbackoff, and thereby allow more data traffic to be accumulated beforethe next TXOP.

With reference now to FIG. 7, a block diagram illustrates a device 700that may be used to delay time as disclosed by the various examplesdiscussed above. The device 700 may be an example of one or more aspectsof the APs 105 or STAs 115 described with reference to FIGS. 1-2, orFIGS. 8-9 as will be described below. The device 700, or portions of it,may also be a processor. The device 700 may include a receiver module710, a delay time module 715, and/or a transmitter module 720. Each ofthese components may be in communication with each other. The device700, through the receiver module 710, the delay time module 715, and/orthe transmitter module 720, may be configured to transmit TXOPsaccording to timing determined based on prior TXOP utilization in orderto transmit TXOPs having higher utilization, similarly as discussedabove with respect to FIGS. 2-6.

Turning to FIG. 8, a diagram 800 is shown that illustrates a STA 115-cconfigured for delay time adjustment based on TXOP utilization accordingto various examples. The STA 115-c may have various other configurationsand may be included or be part of a personal computer (e.g., laptopcomputer, netbook computer, tablet computer, etc.), a cellulartelephone, a PDA, a digital video recorder (DVR), an internet appliance,a gaming console, an e-readers, etc. The STA 115-c may have an internalpower supply (not shown), such as a small battery, to facilitate mobileoperation. The STA 115-c may be an example of the STAs 115 and mayimplement various operations of FIGS. 1-6.

The STA 115-c may include a processor module 805, a memory module 810, atransceiver module 825, antennas 830, and a delay time management module820. The delay time management module 820 may be an example of the delaytime module 715 of FIG. 7. Each of these components may be incommunication with each other, directly or indirectly, over one or morebuses for example.

The memory module 810 may include RAM and ROM. The memory module 810 maystore computer-readable, computer-executable software (SW) code 815containing instructions that are configured to, when executed, cause theprocessor module 805 to perform various functions described herein fordelay time adjustments. Alternatively, the software code 815 may not bedirectly executable by the processor module 805 but be configured tocause the computer (e.g., when compiled and executed) to performfunctions described herein.

The processor module 805 may include an intelligent hardware device,e.g., a CPU, a microcontroller, an ASIC, etc. The processor module 805may process information received through the transceiver module 825and/or to be sent to the transceiver module 825 for transmission throughthe antennas 830. The processor module 805 may handle, alone or inconnection with the delay time management module 820, various aspectsfor TXOP utilization and delay time adjustment based on TXOP utilizationas described herein.

The transceiver module 825 may be configured to communicatebi-directionally with APs 105 in FIGS. 1-2. The transceiver module 825may be implemented as one or more transmitter modules and one or moreseparate receiver modules. The transceiver module 825 may include amodem configured to modulate the packets and provide the modulatedpackets to the antennas 830 for transmission, and to demodulate packetsreceived from the antennas 830. While the STA 115-c may include a singleantenna, there may be examples in which the STA 115-c may includemultiple antennas 830.

The components of the STA 115-c may be configured to implement aspectsdiscussed above with respect to FIGS. 2-7, and those aspects may not berepeated here for the sake of brevity. Moreover, the components of theSTA 115-c may be configured to implement aspects discussed below withrespect to FIGS. 9-13, and those aspects may not be repeated here alsofor the sake of brevity.

Turning to FIG. 9, a diagram 900 is shown that illustrates an AP 105-cconfigured for delay time management according to various examples. Insome examples, the AP 105-c may be an example of the APs 105 of FIGS.1-2. The AP 105-c may include a processor module 910, a memory module920, a transceiver module 930, antennas 940, and a delay time controlmodule 945. The delay time control module 945 may be an example of thedelay time module 715 of FIG. 7. In some examples, the AP 105-c may alsoinclude one or both of an APs communications module 980 and a networkcommunications module 985. Each of these components may be incommunication with each other, directly or indirectly, over one or morebuses 915.

The memory module 920 may include random access memory (RAM) andread-only memory (ROM). The memory module 920 may also storecomputer-readable, computer-executable software (SW) code 925 containinginstructions that are configured to, when executed, cause the processormodule 910 to perform various functions described herein for delay timemanagement by an AP (e.g., TXOP limits, delay time adjustment followingunderutilized TXOPs per access class, etc.). Alternatively, the softwarecode 925 may not be directly executable by the processor module 910 butbe configured to cause the computer, e.g., when compiled and executed,to perform functions described herein.

The processor module 910 may include an intelligent hardware device,e.g., a central processing unit (CPU), a microcontroller, anapplication-specific integrated circuit (ASIC), etc. The processormodule 910 may process information received through the transceivermodule 930, the APs communications module 980, and/or the networkcommunications module 985. The processor module 910 may also processinformation to be sent to the transceiver module 930 for transmissionthrough the antennas 940, to the APs communications module 980, and/orto the network communications module 985. The processor module 910 mayhandle, alone or in connection with delay time control module 945,various aspects related to delay time management and adjustment asdiscussed above.

The transceiver module 930 may include a modem configured to modulatethe packets and provide the modulated packets to the antennas 940 fortransmission, and to demodulate packets received from the antennas 940.The transceiver module 930 may be implemented as one or more transmittermodules and one or more separate receiver modules. The transceivermodule 930 may be configured to communicate bi-directionally, via theantennas 940, with one or more STAs 115 as illustrated in FIG. 1 or FIG.12, for example. The AP 105-c may typically include multiple antennas940 (e.g., an antenna array). The AP 105-c may communicate with a corenetwork 905 through the network communications module 985. The AP 105-cmay communicate with other APs, such as the AP 105-i and the AP 105-j,using an AP communications module 980.

According to the architecture of FIG. 9, the AP 105-c may furtherinclude a communications management module 940. The communicationsmanagement module 940 may manage communications with STAs and/or otherdevices as illustrated in the WLAN network 100 of FIG. 1, for example.The communications management module 940 may be in communication withsome or all of the other components of the AP 105-c via the bus or buses915. Alternatively, functionality of the communications managementmodule 940 may be implemented as a component of the transceiver module930, as a computer program product, and/or as one or more controllerelements of the processor module 910.

The components of the AP 105-c may be configured to implement aspectsdiscussed above with respect to FIGS. 2-8, and those aspects may not berepeated here for the sake of brevity. Moreover, the components of theAP 105-c may be configured to implement aspects discussed below withrespect to FIGS. 10-13 and those aspects may not be repeated here alsofor the sake of brevity.

Turning next to FIG. 10, a flow diagram is described for a method 1000for delay time adjustment based on TXOP utilization in accordance withvarious examples. The method 1000 may be implemented using, for example,STAs 115 of FIG. 1-2 or 8; or the device 700 of FIG. 7. As shown in thefigure, the method begins at block 1005, with the STA determining autilization of a transmit opportunity (TXOP) during a transmission ofdata from a wireless communication device. At block 1010, the STA mayadjust a delay time for a subsequent transmission from the wirelesscommunication device responsive to the determining. In some examples,similarly as described above, the STA may adjust a CW, a backoff time,and/or a number of backoffs, for example, based on TXOP utilization toenhance the efficiency of the wireless communications system.

Turning next to FIG. 11, a flow diagram is described for a method 1100for delay time adjustment in accordance with various examples. Themethod 1100 may be implemented using, for example, STAs 115 of FIG. 1-2or 8; or the device 700 of FIG. 7. As shown in the figure, the methodbegins at block 1105, with the STA determining a maximum duration of thetransmit opportunity TXOP. The STA then may determine a time durationduring which data is transmitted during a transmit opportunity (TXOP),according to block 1110. At block 1115, the STA may determine a ratio ofthe time duration and the maximum duration. Finally, at block 1120, theSTA may adjust a delay time for a subsequent transmission from thewireless communication device based on the ratio. According to someexamples, such as discussed above, delay time may be adjusted byadjusting the CW for one or more subsequent TXOPs by scaling the CWaccording to the utilization ratio of the previous TXOP. In otherexamples, such as discussed above, the STA may be required to performone or more additional backoffs before initiating a next TXOP when aprevious TXOP was underutilized. In further examples, also discussedabove, the STA may increase an average backoff value before initiating anext TXOP when a previous TXOP was underutilized. Following a certainnumber of TXOPs that are more fully utilized, the delay time may bedecreased to a lower value.

Turning next to FIG. 12, a flow diagram is described for a method 1200for delay time adjustment based on TXOP utilization in accordance withvarious examples. The method 1200 may be implemented using, for example,the STAs 115 of FIG. 1-2 or 8; or the device 700 of FIG. 7, for example.As shown in the figure, the method begins at block 1205, with the STAdetermining a utilization of a transmit opportunity (TXOP) during atransmission of data. At block 1210, the STA may increase the delay timevalue by a first amount when the utilization is less than apredetermined utilization. At block 1215, the STA may increase the delaytime value by a second amount when the utilization of a subsequent TXOPis less than the predetermined utilization. Thus, this method providesthat the delay time may be adjusted in two (or more) steps based on TXOPutilization. Following a certain number of TXOPs that are more fullyutilized, the delay time may be decreased, in one or more steps, to alower, or minimum, value.

Turning next to FIG. 13, a flow diagram is described for a method 1300for delay time management based on TXOP utilization in accordance withvarious examples. The method 1300 may be implemented using, for example,the APs 105 of FIG. 1-2 or 9; or the device 700 of FIG. 7, for example.At block 1305, the AP may determine a number of STAs accessing an AP fordifferent ACs. At block 1310, the AP may set an initial delay time, suchas through setting an initial CW value, for STA access to the wirelesschannel for STAs with underutilized TXOPs according to each AC. Forexample, an AP may determine that current traffic conditions aresignificantly less than the total capacity of the AP, and may setinitial CWs to be a relatively low value or to simply be CWmin. In othercases, the AP may determine that current traffic conditions areapproaching the maximum capacity of the AP, and may accordingly setinitial CWs to be a higher value in order to attempt to reduceunderutilized TXOPs and reduce contention between STAs and therebyenhance the utilization of the wireless medium. Finally, at block 1315,the AP may adjust the initial delay time based on changing trafficconditions and/or numbers of STAs accessing the AP. Thus, if trafficconditions change from the AP having a significant amount of availablecapacity to a relatively small amount of available capacity, the AP mayadjust the delay time for STAs following underutilized TXOPs in order toreduce underutilized TXOPs.

The detailed description set forth above in connection with the appendeddrawings describes exemplary examples and does not represent the onlyexamples that may be implemented or that are within the scope of theclaims. The term “exemplary” when used in this description means“serving as an example, instance, or illustration,” and not “preferred”or “advantageous over other examples.” The detailed description includesspecific details for the purpose of providing an understanding of thedescribed techniques. These techniques, however, may be practicedwithout these specific details. In some instances, well-known structuresand devices are shown in block diagram form in order to avoid obscuringthe concepts of the described examples.

Information and signals may be represented using any of a variety ofdifferent technologies and techniques. For example, data, instructions,commands, information, signals, bits, symbols, and chips that may bereferenced throughout the above description may be represented byvoltages, currents, electromagnetic waves, magnetic fields or particles,optical fields or particles, or any combination thereof.

The various illustrative blocks and modules described in connection withthe disclosure herein may be implemented or performed with ageneral-purpose processor, a digital signal processor (DSP), anapplication specific integrated circuit (ASIC), a field programmablegate array (FPGA) or other programmable logic device, discrete gate ortransistor logic, discrete hardware components, or any combinationthereof designed to perform the functions described herein. Ageneral-purpose processor may be a microprocessor, but in thealternative, the processor may be any conventional processor,controller, microcontroller, or state machine. A processor may also beimplemented as a combination of computing devices, e.g., a combinationof a DSP and a microprocessor, multiple microprocessors, one or moremicroprocessors in conjunction with a DSP core, or any other suchconfiguration.

The functions described herein may be implemented in hardware, softwareexecuted by a processor, firmware, or any combination thereof. Ifimplemented in software executed by a processor, the functions may bestored on or transmitted over as one or more instructions or code on acomputer-readable medium. Other examples and implementations are withinthe scope of the disclosure and appended claims. For example, due to thenature of software, functions described above can be implemented usingsoftware executed by a processor, hardware, firmware, hardwiring, orcombinations of any of these. Features implementing functions may alsobe physically located at various positions, including being distributedsuch that portions of functions are implemented at different physicallocations. Also, as used herein, including in the claims, “or” as usedin a list of items prefaced by “at least one of” indicates a disjunctivelist such that, for example, a list of “at least one of A, B, or C”means A or B or C or AB or AC or BC or ABC (i.e., A and B and C).

Computer-readable media includes both computer storage media andcommunication media including any medium that facilitates transfer of acomputer program from one place to another. A storage medium may be anyavailable medium that can be accessed by a general purpose or specialpurpose computer. By way of example, and not limitation,computer-readable media can comprise RAM, ROM, EEPROM, CD-ROM or otheroptical disk storage, magnetic disk storage or other magnetic storagedevices, or any other medium that can be used to carry or store desiredprogram code means in the form of instructions or data structures andthat can be accessed by a general-purpose or special-purpose computer,or a general-purpose or special-purpose processor. Also, any connectionis properly termed a computer-readable medium. For example, if thesoftware is transmitted from a website, server, or other remote sourceusing a coaxial cable, fiber optic cable, twisted pair, digitalsubscriber line (DSL), or wireless technologies such as infrared, radio,and microwave, then the coaxial cable, fiber optic cable, twisted pair,DSL, or wireless technologies such as infrared, radio, and microwave areincluded in the definition of medium. Disk and disc, as used herein,include compact disc (CD), laser disc, optical disc, digital versatiledisc (DVD), floppy disk and blu-ray disc where disks usually reproducedata magnetically, while discs reproduce data optically with lasers.Combinations of the above are also included within the scope ofcomputer-readable media.

The previous description of the disclosure is provided to enable aperson skilled in the art to make or use the disclosure. Variousmodifications to the disclosure will be readily apparent to thoseskilled in the art, and the generic principles defined herein may beapplied to other variations without departing from the scope of thedisclosure. Throughout this disclosure the term “example” or “exemplary”indicates an example or instance and does not imply or require anypreference for the noted example. Thus, the disclosure is not to belimited to the examples and designs described herein but is to beaccorded the widest scope consistent with the principles and novelfeatures disclosed herein.

What is claimed is:
 1. A method for wireless communications, comprising:determining a utilization of a transmit opportunity (TXOP) during atransmission of data from a wireless communication device; adjusting adelay time for a subsequent transmission from the wireless communicationdevice based at least in part on the determined utilization, whereinadjusting the delay time comprises one from the group consisting of:increasing the delay time when the utilization is less than a firstpredetermined utilization; and decreasing the delay time when theutilization is greater than a second predetermined utilization; andwherein adjusting the delay time comprises adjusting an initialcontention window (CW) value for the subsequent transmission.
 2. Themethod of claim 1, wherein adjusting the delay time further comprises:adjusting a parameter selected from the group consisting of: a backoffvalue for the subsequent transmission, or a number of backoffs beforeinitiating the subsequent transmission.
 3. The method of claim 1,wherein adjusting the delay time comprises: decreasing the delay timewhen the utilization is greater than the second predeterminedutilization and the utilization of a predetermined number of previousTXOPs are each greater than the second predetermined utilization.
 4. Themethod of claim 1, wherein the determining comprises determining a timeduration during which data is transmitted during the TXOP, wherein theadjusting the delay time comprises increasing the delay time when thetime duration is shorter than a predetermined time duration.
 5. Themethod of claim 1, wherein the determining comprises: determining amaximum duration of the TXOP; determining a time duration during whichdata is transmitted during the TXOP; and determining a ratio of the timeduration and the maximum duration.
 6. The method of claim 5, whereinadjusting the delay time comprises: increasing the delay time when theratio is less than a predetermined ratio.
 7. The method of claim 1,wherein adjusting the delay time comprises: adjusting the delay time toallow for accumulation of additional data prior to the subsequenttransmission relative to an amount of data accumulated using anunadjusted delay time.
 8. The method of claim 1, wherein adjusting thedelay time comprises: scaling the delay time according to theutilization of the TXOP.
 9. The method of claim 1, wherein adjusting thedelay time comprises: increasing the delay time by a first amount whenthe utilization is less than the first predetermined utilization; andincreasing the delay time by a second amount when the utilization of asubsequent TXOP is less than the first predetermined utilization. 10.The method of claim 1, further comprising: determining a secondutilization of a subsequent TXOP during the subsequent transmission fromthe wireless communication device; and re-adjusting the delay timeresponsive to the utilization and the second utilization.
 11. The methodof claim 10, wherein the re-adjusting the delay time comprises:resetting the delay time to a minimum value when the second utilizationis greater than a third predetermined utilization.
 12. The method ofclaim 10, wherein the re-adjusting the delay time comprises: furtherincreasing the delay time when the second utilization is less than afourth predetermined utilization.
 13. An apparatus for wirelesscommunications, comprising: means for determining a utilization of atransmit opportunity (TXOP) during a transmission of data from awireless communication device; means for adjusting a delay time for asubsequent transmission from the wireless communication device based atleast in part on the determined utilization, wherein the means foradjusting the delay time comprises one from the group consisting of:means for increasing the delay time when the utilization is less than afirst predetermined utilization; and means for decreasing the delay timewhen the utilization is greater than a second predetermined utilization;and wherein adjusting the delay time comprises adjusting an initialcontention window (CW) value for the subsequent transmission.
 14. Theapparatus of claim 13, wherein the means for adjusting the delay timefurther comprises means for adjusting a parameter selected from thegroup consisting of: a backoff value for the subsequent transmission ora number of backoffs before initiating the subsequent transmission. 15.The apparatus of claim 13, wherein the means for adjusting the delaytime comprises: means for decreasing the delay time when the utilizationis greater than the second predetermined utilization and the utilizationof a predetermined number of previous TXOPs are each greater than thesecond predetermined utilization.
 16. The apparatus of claim 13, whereinthe means for determining comprises means for determining a timeduration during which data is transmitted during the TXOP; and whereinthe means for adjusting the delay time comprises means for increasingthe delay time when the time duration is shorter than a predeterminedtime duration.
 17. The apparatus of claim 13, wherein the means fordetermining comprises: means for determining a maximum duration of theTXOP; means for determining a time duration during which data istransmitted during the TXOP; and means for determining a ratio of thetime duration and the maximum duration.
 18. The apparatus of claim 13,wherein the means for adjusting the delay time comprises: means foradjusting the delay time to allow for accumulation of additional dataprior to the subsequent transmission relative to an amount of dataaccumulated using an unadjusted delay time.
 19. The apparatus of claim13, wherein the means for adjusting the delay time comprises: means forscaling the delay time according to the utilization of the TXOP.
 20. Theapparatus of claim 13, wherein the means for adjusting the delay timecomprises: means for increasing the delay time by a first amount whenthe utilization is less than the first predetermined utilization; andmeans for increasing the delay time by a second amount when theutilization of a subsequent TXOP is less than the first predeterminedutilization.
 21. The apparatus of claim 13, further comprising: meansfor determining a second utilization of a subsequent TXOP during thesubsequent transmission from the wireless communication device; andmeans for re-adjusting the delay time responsive to the utilization andthe second utilization.
 22. The apparatus of claim 21, wherein the meansfor re-adjusting the delay time comprises: means for resetting the delaytime to a minimum value when the second utilization is greater than athird predetermined utilization; and means for further increasing thedelay time when the second utilization is less than a fourthpredetermined utilization.
 23. An apparatus for wireless communication,comprising: a transmitter configured to transmit data to an access pointduring a transmit opportunity (TXOP); a delay time manager configured todetermine a utilization of the TXOP during the transmission of data froma wireless communication device and adjust a delay time value for asubsequent transmission responsive to the determining, wherein adjustingthe delay time comprises one from the group consisting of: increasingthe delay time when the utilization is less than a first predeterminedutilization; and decreasing the delay time when the utilization isgreater than a second predetermined utilization; and wherein adjustingthe delay time comprises adjusting an initial contention window (CW)value for the subsequent transmission.
 24. The apparatus for wirelesscommunication of claim 23, wherein the adjusting the delay time furthercomprises: adjusting a parameter selected from the group consisting of:a backoff value for the subsequent transmission or a number of backoffsbefore initiating the subsequent transmission.
 25. A non-transitorycomputer-readable medium comprising computer-readable program codestored thereon, the computer-readable program code when executed by atleast one processor to cause the at least one processor to: determine autilization of a transmit opportunity (TXOP) during a transmission ofdata from a wireless communication device; adjust a delay time for asubsequent transmission from the wireless communication device based atleast in part on the determined utilization, wherein the code to causethe at least one processor to adjust the delay time further comprisesone from the group consisting of: code to cause the at least oneprocessor to increase the delay time when the utilization is less than afirst predetermined utilization; and code to cause the at least oneprocessor to decrease the delay time when the utilization is greaterthan a second predetermined utilization; and wherein adjusting the delaytime comprises adjusting an initial contention window (CW) value for thesubsequent transmission.
 26. The non-transitory computer-readable mediumof claim 25 wherein the computer-readable program code further causesthe at least one processor to adjust a parameter selected from the groupconsisting of: a backoff value for the subsequent transmission, or anumber of backoffs before initiating the subsequent transmission.